Messages

21

General Mach Discussion / Re: Mach 3 - driving beyond soft limits ?

« on: April 08, 2018, 04:36:00 AM »

Davek0974, two such occurrences in one year, on the same 2H - long job. 

22

General Mach Discussion / Re: Mach 3 - driving beyond soft limits ?

« on: April 08, 2018, 04:33:27 AM »

Craig, Davek0974, thank you both for helping.

I'm also skeptical about Mach 3 having such a bug, its been around for long, and why would it show-up after a year of regular operation on the same rig, a dedicated PC that receives MINIMAL maintenance and changes.

Vdc and I at PSU seem OK.  Motor couplers OK. Temp of one axis a bit high, to my taste.

Monitoring pulse trains on a 4 channel scope, pretty boring pattern, using its memory to keep as much data as possible. Figuring out a way to have the scope halt acquisition after a failure. 

23

General Mach Discussion / Re: Mach 3 - driving beyond soft limits ?

« on: April 08, 2018, 01:56:52 AM »

Good morning / evening Joeaverage alias Craig, thank you for your input.

"Were you observing the machine while it was working ?"

no, it was a long job, and I was doing something else. But we are now having a team (+ video recording) and hope to be able to observe this type of event.

"Could it have suddenly stopped and only start again after the code had 'moved on' by 170mm ?"

on this job, surfacing, there are X stops at the end of each travel, a dY to move the tool and a reverse command to the starting X point. The legs on X are always 700.0 mm long, there is no "170 long move" in the code anywhere. I feel 170 could have been anything, same for the 23 mm.  The only "known" stop is when the screen of the PC dims, there is a short interruption, but it is a clean one; machine and Mach 3 remain sync. This event is known and way too short to produce such gaps.

"Could the machine be losing steps incrementally but only show up when a move was called that moved out-of-bounds ? "
 
Loosing step is an obvious candidate, but no smoking gun yet.

Enjoy this nice day, Philippe

24

General Mach Discussion / Re: Mach 3 - driving beyond soft limits ?

« on: April 07, 2018, 09:05:27 AM »

Howdy Davek0974, thank you for this thought.

We are trying to reproduce the issue, one axis at the time, by disabling two out of three axis, no work piece.
Jamming does not seem a good candidate; when we disconnect the spindle (design on Y and X made on purpose for easy disconnection) they slide freely.   What we hope for now is something like "slipping".  If the stepper misses steps or swallows a few,  i.e. the axis does not move as much as expected and Mach3 will not know about it. This could also result in a shift. No smoking gun yet ! and the sun shines outside ... But these jobs must be ready by Monday ...

Philippe

25

General Mach Discussion / Re: Mach 3 - driving beyond soft limits ?

« on: April 07, 2018, 05:54:04 AM »

TPS, thank you.

Yes, "softlimits" is always on for regular machining.

(Ansonsten waere ich ein bischen der Depp gewesen, alles erklaeren und genau das zu vergessen, oder nicht ?)

Enjoy the nice spring day, Philippe

26

General Mach Discussion / Mach 3 - driving beyond soft limits ?

« on: April 07, 2018, 03:25:35 AM »

Dear Forum Readers,

Has anyone else experienced something similar

I have been using Mach 3 for about a year for prototyping work on a 1 meter x 1.5 meter 3 axis router system, without major problems.

Two recent events are suspicious and potentially dangerous; Mach 3 passed one of its soft limits during machining and the axis motion was stopped by the hardware limit switch in place. These two scary events were started in a regular manner, no warning of Mach 3 telling me that the job goes beyond a soft limit, for example.   

On the second such event I could verify that the machine coordinate system of two axis had shifted by some amount, 170 mm for one axis, some 23 mm for the second.

I extracted these two numbers by jogging the "crashed" axis off of the limit and gently jogging to each of the home switches until they trip. The values indicated by the DROs in this situation should be identical than the values after a homing procedure, zero in my case.  A clear shift in machine coordinate was present. Scary and disappointing.

The configuration of this basic 3 axis open loop system:
X, stepper, no encoder, home switch on its own pin, limits in series on pin 15
A is slave of Y, steppers, no encoders,  Y home switch on its own pin, Y limits in series on pin 15
Z, stepper, no encoder, home switch on its own pin, Z limits in series on pin 15
in short: 3 pins for homing, one for limits, and one for e-stop.
The working volume defined by the soft limits is smaller and lies inside the volume defined by the hardware limits.

Any comment you may provide will be appreciated.

enjoy your WE, Philippe

27

General Mach Discussion / Re: Homing operation does not pulls back enough to get away from switch?

« on: April 06, 2018, 10:58:48 AM »

Gerry, you are absolutely right, its called kinetic energy, the exact amount of which must be dissipated by the "stop" or some sort of "brake".

28

General Mach Discussion / Re: Homing operation does not pulls back enough to get away from switch?

« on: April 06, 2018, 08:38:55 AM »

this is today the second event of Mach3 driving BEYOND one of the soft limits. Crash, minor damage. Thank you hardware limits, mounted and wired separately from the homing devices, etc. Driving axis off of limit, cleaning up the mess, and jogging to the home of this particular axis shows a shift of dY = 180 mm, in MACHINE COORDINATES and a minor
dX of 23 mm.

Now, if for some reason, the machine coordinate value of one axis shifts by a certain amount, the soft limit will trigger before or after, depending on the sign of the shift.

Which mechanism can produce such a shift ?
Am I the only fellow with this issue ?

Two events of that sort in one week after more than a year of smooth operation is a good statistics ... waiting for a shift in Z !!

Comments are welcome.

Philippe

29

General Mach Discussion / Re: Homing operation does not pulls back enough to get away from switch?

« on: April 05, 2018, 11:41:10 AM »

Good evening Tweakie, yes, my license is registered in my name, no cheating. I suppose you are asking about the "strange shift".

I'm trying to reproduce this unique (but scary) event, but have failed thus far.  The job ROI was well confined within range defined by the soft limits. I was not next to the rig when it happened, but I heard the "crash" in one of the supports. I ran to the machine and saw one support holding the work piece pulled off, and the machine nicely going further  with a lateral shift of about 200 mm. On the next direction change (surfacing job) it passed soft limits and was stopped by HW limits that I have wired SEPARATELY from the homing devices, as Colleague "joeaverage" advertises vehemently.

Enjoy your day/evening, Philippe   

30

General Mach Discussion / Re: Homing operation does not pulls back enough to get away from switch?

« on: April 04, 2018, 04:25:51 PM »

Davek0974, all right, your argument leverages on the "limited" power of stepper motors AND on the presence of sufficiently strong end stops.

Here the story of a (thus far unique) unexplained event that convinces me to combine HW AND soft limits on a open loop rig without encoders. On a long job, about a square meter of working area, one axis gets a sudden shift of about 200 mm. I double checked (after the "crash" into the support) that this shift WAS NOT in the G-code in the form of a global or fixture offset. The axis passed beyond it SW limit (don't ask me why/how) and was stopped by the hardware limit switch placed 3 cm before the physical limit of this axis.
Without this switch, I agree that the damage (to the machine) would have been limited, but the job would not have stopped and the work piece would have been wasted.

Has anyone else experienced "sudden unexplained" shifts ?